The invention concerns a dead-end filtration unit for the selective separation of fluid substances with porous membrane adsorbers. The unit is useful for the selective separation and purification of materials which exhibit a specific affinity for adsorption such as heavy metals, bio-specific molecules, proteins, enzymes and ionized substances, and finds application in the fields of biotechnology, genetics, environmental clean-up, pharmaceuticals, analytical chemistry as well as in the food and drink industries.
According to PCT Patent Application No. 92/00805, porous adsorber membranes are such membranes as carry on their surface functional groups, ligands or reactants, which are interactive with at least one substance which is in contact with them in the fluid phase. Transport of the fluid phase through the membrane is by convection. The term "membrane adsorber" is understood in the art as a general term for membrane ion exchangers, ligand membranes and activated membranes. These in turn are subdivided according to their functional groups, ligands and reactants.
U.S. Pat. No. 4,895,806 discloses a filtration unit for the separation of molecular components from fluid mixtures by membrane adsorbers, comprising a housing, a plurality of membrane discs separated into groups by washers, with the entire membrane disc assembly being compressed between compression rings, wherein the peripheries of the compression rings and washers are in contact with the wall of the housing so as to provide a seal to prevent leakage between the membranes and the housing wall. The disadvantages of such a design are (1) when a smaller number of membrane adsorber discs are used, the unit's adsorption capacity is too low, and (2) when a greater number of membrane discs are used, the unit suffers from an exponentially restricted flow rate, even at higher pressures. A further disadvantage is that, because of the relative permanency of the seal, the membrane adsorber type within the housing is unchangeable and the user of that type of filtration unit cannot separate different materials with a single filtration unit during a single filtration run.
Important objects of the present invention include the provision of a dead-end membrane adsorber filtration unit characterized by a minimal dead volume, by a capability for scale-up, and that has the capability of simultaneous separation of different materials during a single filtration run. These objects and others that will become apparent to one of ordinary skill are achieved by the dead-end membrane adsorber filtration unit of the present invention which is summarized and described in detail below.